For decades researchers have been working to increase storage density and reduce storage cost of data storage devices such as magnetic hard drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult because conventional technologies appear to be approaching fundamental limits on storage density. For instance, data storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, below which magnetic bits are not stable at room temperature.
Storage devices that do not face these fundamental limits are being researched. An example of such an information storage device is described in Choi et al. U.S. Patent Application Publication Ser. No. 2002/0066855 A1 (the “Publication”). According to the Publication, an apparatus for recording and reading data includes a contact probe and a storage medium. In one embodiment, the storage medium is formed from a substrate, a conductive layer on the substrate, and a dielectric layer on the conductive layer. The probe records data in the storage medium by forming holes in the dielectric layer. The holes expose the surface of the conductive layer. During read operations, the probe is scanned across the storage medium. When the tip of the probe encounters a hole, the tip falls into the hole, and a short occurs between the probe tip and conductive layer.
The Publication acknowledges that abrasion of the probe tip is a problem with the first embodiment. The abrasion can occur during read and write operations, when the probe tip makes contact with the conductive layer. The abrasion causes the tip to wear. The wear can shorten the life of the storage device.
The Publication discloses a second embodiment, in which the storage medium is formed from a substrate and a conductive polymeric layer on the substrate. Data is recorded by forming holes in the conductive polymeric layer. The data is read by scanning the probe is scanned across the conductive polymeric layer. A short between the tip and the conductive polymeric layer is supposed to occur when the probe passes over the conductive polymeric layer; and a short is not supposed to occur when the tip passes over a hole. The Publication claims that the second embodiment reduces abrasion of the tip and has a fast data read speed.